This invention relates generally to tuning mechanisms, and more particularly to detented type "memory" tuning systems for UHF television tuners.
Several techniques for providing detent type UHF television tuners are known. Several such systems are described in U.S. Pat. Nos. 3,774,459 issued Nov. 27, 1973 to A. A. Valdettaro; U.S. Pat. No. 3,757,227 issued Sep. 4, 1973 to M. L. Weigel; 3,188,871 issued June 15, 1965 to R. E. Mentzer; U.S. Pat. No. 3,697,904 issued Oct. 10, 1972 to E. Mohri et al.; and U.S. Pat. No 3,205,720 issued Sep. 14, 1965 to T. D. Smith. An example of a commercial memory type VHF tuner is the RCA KRK 72 RVS 8242 3. A memory type UHF tuner has also been built by German Phillips Ltd. The Phillips tuner is described in an article by J. Korn entitled "Neuartige Abstimmhilfen fur UHF" appearing in "FUNKSCHAU", Vol. 12, p. 326, 1962.
Whereas these systems provide detent type UHF tuners, the Valdettaro patent does not provide a memory type fine tuning system. A memory type fine tuning system is a system wherein each channel (or group of adjacent channels) has an independent fine tuning mechanism for providing independent fine tuning of each channel, the setting of which is maintained despite changes in channel selection. Other prior art systems provide memory type fine tuning, however, because the fine tuning mechanism is tunable over three channels and also serves as a channel selector, the resettability of each channel is marginal, and generally some degree of fine tuning adjustment is required after each channel change. Furthermore, the channel number displayed is not independent of the position of the fine tuning control, and a unique indication of the channel number is not provided.
Modern VHF tuners, such as the RCA unit referenced above, utilize a turret or a switch type tuner that has inherent detent positions. As a result, the problems encountered in converting the continuously variable motion of a UHF tuner to detented operation do not arise.
The Phillips UHF tuner is designed for the European UHF band and employs a separate fine tuning element for each UHF channel. Such a system is usable in Europe because the European UHF band contains only 40 channels. In the United States, where 70 UHF channels are provided, the use of a separate tuning element for each channel would result in a structure so large and complex as to be impractical.
Accordingly, it is an object of the present invention to provide a UHF tuning system wherein each detent position of the selector shaft corresponds to a different UHF channel, and wherein a memory type fine tuning mechanism is provided to allow independent fine tuning of groups of channels lying in adjacent detent tuning positions.
It is another object of the present invention to provide a detented UHF memory type tuning mechanism having a digital readout that uniquely displays the channel number corresponding to each channel independently of the setting of the fine tuning mechanism.
A further object of the present invention is to provide a detent type UHF tuning mechanism having a memory tape fine tuning mechanism tunable over the frequency range of one television channel.
Still another object of the present invention is to provide a detented memory type UHF tuner mechanism wherein the range of UHF television channels is covered by more than one revolution of the selector shaft, and wherein each channel in the tuning range is covered by a different one of the detented positions.